The silicon photonics platform, with its ability to manifest photonic devices, is promising for use in next-generation optical circuits and links. However, as the high-performance functionality of both passive and active silicon devices have continued to be demonstrated, concerns have grown over performance degradation with ambient temperature variations due to the high thermo-optic coefficient of Silicon (˜1.86*10^−4/K). To achieve the future vision of high bandwidth at low cost, it is necessary to develop technologies that will reduce the temperature sensitivity of silicon photonics.
Thermal stabilization of photonic devices, such as those containing silicon or other materials comprising high positive thermo-optic coefficients, has been an ongoing challenge. A common approach to the suppression of temperature sensitivity in silicon based chip-scale devices consists of using external heaters or thermoelectric coolers. However, as these approaches are active, they increase power consumption and account for the largest share in a power budget of state-of-the-art silicon photonics, in addition to demanding a large device foot-print and cost. Passive thermal stabilization techniques typically rely on the use of a negative thermo-optic coefficient (TOC) material to offset silicon's high positive TOC. Materials commonly used for passive thermal stabilization consist of polymers, such as acrylates (PSQ-LH, Polymethyl methacrylate), or Exguide™ LFR-372 (ChemOptics Inc.). A drawback to polymers, however, is that they are vulnerable to temperature degradation, chemical instability, UV aging, and poor mechanical characteristics.
Current strategies for temperature stabilization of photonic devices, such as silicon-based photonic devices, include local heating of the device itself to dynamically compensate for any temperature fluctuations, but this scheme is both cumbersome (requiring thermoelectric coolers and controllers) and power hungry. Other methods consist of using a WIR30-490 polymer overlay cladding which has negative thermo-optic coefficient, but this approach is not CMOS compatible as WIR30-490 cannot undergo any subsequent high temperature processes. Consequently, there is a growing need for compensation of the thermo-optic effect in silicon photonics.